1. Field the Invention
The present invention relates, generally, to core drills for sampling mineral specimens or the like and, more especially, to a portable core drill for this purpose which may be transported with relative ease even to very remote locations.
2. Description of the Background Art
Myriad endeavors require core sampling in order to extract a specimen from a larger mass for the purpose of ascertaining the physical and/or chemical morphology of the latter. All manner of materials are sampled in this way, ranging from relatively loosely compacted substances (e.g., soil) through extremely dense mineral substances (e.g., granite). It is with respect to the denser materials from which cores are extracted that the instant invention particularly pertains.
Geological studies, particularly paleomagnetic research, include core sampling techniques as a mainstay of the scientific undertaking. The core drills employed to obtain core specimens from large mineral formations are all characterized by certain general features. The drill bit utilized is typically a tubular steel member, sometimes stainless steel, tipped with a peripheral circumferential abrading element, usually in the form of a ring of a matrixed diamond abrasive or other suitable abrasive substance. The tubular drill bit is rotated about a drill axis and urged against and thence into the dense mass (e.g., granite); the bit then withdrawn and the specimen snapped from the parent mass. Normally, the drill bit is cooled with a fluid coolant which might simply be water or which might also include a lubricating component, such as a water-soluble oil, antifreeze or another drilling adjuvant dictated by the circumstances.
Where such rock sampling is undertaken in areas accessible by roadways, the survey team is usually not unduly limited in the types of drive motors or engines which might be employed to impart drilling-effective rotary motion to the drill bit. However, a substantial effort has been and continues to be made in the geological studies of rock morphology in very remote regions. It is now common for a survey team to hike many days into very remote areas to conduct these studies. This places considerable demands on the type of equipment which might be employed for core sampling. For example, the core drill must be as compact and as light and as free of required tools as possible so that it may be carried to these remote locations with minimum difficulty or discomfort, oftentimes through very difficult terrain. On the other hand, durability and reliability in operation cannot be sacrificed for portable mobility.
Some efforts have been made to meet these needs and, to varying extents, some goals have been achieved. Perhaps one of the more significant steps toward providing a durable and reliable portable core drill has been the relatively recent adaptation of chain saw engines as the drive member for the drill. It is now possible to obtain a chain saw engine which weights as little as about 8 to 9 pounds and yet one which can deliver sufficient power to operate the drill. Various adapters to couple the drill bit to the chain saw engine have been devised to convert the engine to a useable drive for a drill.
One approach in the design of a coupling member has simply been to weld or otherwise secure a nut on the end of the tubular drill and thread the nut/bit assembly onto a mating coupler on the engine. This approach suffers somewhat for a number of reasons limiting the desirability of the technique. First, even tedious layup rarely insures complete concentricity and squareness of the nut as respects the drill axis. Hence, a wobbling motion may be imparted during the drilling operation which at least is undesirable but which may also contribute significantly to excessive wear and vibration of the bit and motor assembly. Second, this approach necessitates carrying tools for assembly and disassembly thereby adding to the weight of the load to be carried and a significant inconvenience in operation. Third, the proximal nut typically obstructs the interior of the drill bit, making removal of a broken core specimen an inconvenient task.
Another suggestion has incorporated a type of rubber-flex collet to couple the drill bit to the drive engine. This approach improves on the ability to align the drill concentrically but the structure employed in this type of device nonetheless requires one to carry tools in order to assemble and disassemble the drill components. Overall, the core drill is bulky and heavy, limiting its desirability.
Other problems pervade the use of existing devices for core sampling. For example, it is always desirable and sometimes mandatory to provide a coolant fluid, which might also act as a lubricant, to the drill bit during operation. It is most desirable to be able to inject or otherwise transmit the fluid along and throughout the annular path of the tool bit. While this can sometimes be achieved externally of the drill itself, as by application of fluid to the outer surfaces of the drill bit during operation, it is better to introduce this coolant/lubricant internally and allow the same to escape externally of the drill bit. This provides improved cooling and lubricating characteristics during operation and also aids in carrying away or flushing particle debris from the active drilling point. To achieve this goal, the fluid should somehow be introduced to the drill bit through the coupling member. In some designs, where the coupling member rotates, this can be a difficult task to perform. In every design, however, it is important to maintain fluid integrity of the coupler so that all operating components are fluid-sealed. This has yet to be realized as a practical matter.
Accordingly, the need still exists to provide a lightweight, compact, yet durable and dependable, portable core drill which requires no tools for assembly or disassembly and yet which includes a drive connector or coupler which may deliver fluid to the drill and which further provides a highly concentric rotary drilling motion as respects the drilling axis.